1. Field of the Invention
The present invention relates to devices for detecting the presence of analytes. In particular, the invention relates to such devices whereby disposable assays may be quickly and efficiently conducted in the field. More particularly, the invention relates to an improved arrangement for mixing reagents used in such devices.
2. The Prior Art
There is a present and continuing need to detect a wide variety of analytes with high specificity and high sensitivity in many applications. A technique that is well known in the art uses antibody/antigen (antibody generator) reactions to determine a target analyte. One common use of the antibody/antigen pair is in the construction of a reaction environment in which microscopic particles to which antibody or antigens have been chemically attached are made to agglutinate or are inhibited from agglutinating in the presence of the mating antibody/antigen and the target analyte.
When an agglutination reaction occurs, the microscopic particles chemically bind to each other with the antibody/antigen molecules serving as very specific chemical binding agents, forming much larger aggregates of particles which can grow in size to become visible to the naked eye. The progress of the reaction may be monitored and resulting data analyzed to provide quantitative and qualitative results on target analyte concentration.
A specific agglutination reaction is latex agglutination. Latex agglutination tests are available which detect small qualities of antigen molecules. Agglutination reactions usually involve the aggregation of latex particles which bear on the surface antigenic molecules. Aggregation (agglutination) occurs when antibody molecules specifically corresponding to the antigen (e.g. cocaine) are introduced into the solution of the carrier particles. Antibodies can be visualized as having a "Y" shape where both arms of the "Y" can attach antigen. Mixing antigen-coated latex particles and antibody causes these components to interact and combine. As more antibodies and particles become involved, many cross-linkages are formed and the particles group together as visible clusters. However, when free, unbounded antigen is introduced from an external sample, for instance, agglutination does not occur. The free antigen caps the antibody binding sites and inhibits the agglutination.
Devices are known in the art which can detect various analytes. However, these devices require numerous steps that are not conducive to being used in the field environment, with minimal training, in a simple sequence, to provide consistent results. An assay device designed for ease of use by the person performing the test would be desirable.
Devices are known which require a user to add the required reagents and perform a crude stirring or mixing operation which is subject to not being repeatable in the field. Carrying the required reagents, measuring the exact proportions, and mixing the reagents in the assay device are steps which are not conducive to ease of use with minimal training. It would be desirable to have an assay device which contained the pre-measured reagents needed to perform a specific test to determine if a suspect substance contained a target analyte. Additionally, it would be desirable to have an assay device which was designed to adequately mix the reagents upon being actuated before being introduced to the sample or suspect substance for further mixing.
Known devices require the assay device to be held still or horizontal while the reagent and sample mixture flow through the assay device to get an agglutination result. Some devices require close tolerances in manufacturing to obtain capillary flow. Other known devices require the white room environment of a laboratory. It would be desirable for operators in the field to have an assay device that could be used by simply placing a sample to be tested into the device with an optimal amount of sample being collected by a swab and triggering an actuator which would quickly and repeatedly carry out the test without room for operator error. It would also be desirable to have a device resistant to an abusive environment of rough handling and jostling around even while the test was being conducted.
This application is related to U.S. Pat. No. 5,290,517 entitled "Optical Agglutination Assay Device", filed Apr. 4, 1990 and assigned to the same assignee as the present application and hereby incorporated by reference. While that patent discloses different design configurations for the assay device, it may be utilized with an optical transmitting and receiving unit for measuring the intensity of light reflected from or transmitted through an optical viewing area in a track as a measure of the occurrence of agglutination in the reaction system.
A simple, inexpensive, portable assay device for detection of an unknown analyte with improved mixing of the requisite reagents used in the device, is disclosed herein.